Flexible plastic parenteral solution containers are presently sold by Travenol Laboratories, Inc. under the trademark VIAFLEX.RTM.. These containers have many substantial advantages over glass bottles of parenteral solution, particularly in their reduced weight, lack of susceptibility to breakage, and freedom from the need to allow air to bubble into the solution container as it drains.
The presently available plastic parenteral solution bags are made of a pair of flat sheets of polyvinyl chloride plastic, heat-sealed at their edges to form a sealed, sterile container. In the past, various attempts have been made to replace the heat-sealed plastic solution containers with blow molded containers. However, one drawback to the use of such blow molded containers is the fact that, when hung from one end with solution being drawn out of them from the other end, they tend to collapse in an incomplete manner. This is particularly so when relative stiff polymers, e.g., polyolefins such as polyethylene or polypropylene, are used.
The reason for this incomplete collapse is that the stiffness of a thin-walled polypropylene container frequently tends to resist collapse to such a degree that the moderate suction pressure exerted on the container by weight of the fluid in an administration set attached to the container is insufficient to cause its complete collapse.
Another disadvantage of certain prior art solution containers made from blow-molded parisons is that they may collapse in a non-uniform manner. On some occasions these devices, which are generally oval in shape, collapse along the long axis of their oval cross-section, but on other occasions they tend to collapse along both the short axis of the cross-section as well as the long axis. As a result of this, it becomes quite difficult for a nurse to determine exactly how much solution has passed out of the solution container.
Also, it is desirable to provide containers for parenteral solution delivery and the like which collapse flat over essentially all of their length, so that the entire liquid contents of the container can be expelled, and only a small, residual amount of air, for example less than 5 percent of the volume of the container, remains therein. The maximum air volume of 5 percent is better appreciated when it is understood that this also approximates the volume of typical parenteral solution administration equipment, when a 1 liter bag is used. This is much superior to semicollapsible containers which exhibit a large air volume of a hundred c.c. or more per liter, avoiding the possibility of large amounts of air entering the solution administration tubing to pass to the patient.
In accordance with this invention, a collapsible parenteral solution container is provided which can advantageously be made of stiffer, more desirable plastic material such as polypropylene, while still being readily completely collapsible in normal therapeutic use as a dispenser of parenteral solution. Also, the novel container of this invention collapses in a uniform manner, which simplifies the determination of the amount of fluid remaining in the container at any time. Likewise, the container can collapse essentially completely under normal suction exerted by the suction head of solution in the administration set.